from typing import Dict

from scipy.stats import chi2

from arch.vendor import cached_property

__all__ = ["WaldTestStatistic"]


class WaldTestStatistic(object):
    """
    Test statistic holder for Wald-type tests

    Parameters
    ----------
    stat : float
        The test statistic
    df : int
        Degree of freedom.
    null : str
        A statement of the test's null hypothesis
    alternative : str
        A statement of the test's alternative hypothesis
    name : str, default "" (empty)
        Name of test
    """

    def __init__(
        self, stat: float, df: int, null: str, alternative: str, name: str = "",
    ) -> None:
        self._stat = stat
        self._null = null
        self._alternative = alternative
        self.df = df
        self._name = name
        self.dist = chi2(df)
        self.dist_name = "chi2({0})".format(df)

    @property
    def stat(self) -> float:
        """Test statistic"""
        return self._stat

    @cached_property
    def pval(self) -> float:
        """P-value of test statistic"""
        return 1 - self.dist.cdf(self.stat)

    @cached_property
    def critical_values(self) -> Dict[str, float]:
        """Critical values test for common test sizes"""
        return dict(zip(["10%", "5%", "1%"], self.dist.ppf([0.9, 0.95, 0.99])))

    @property
    def null(self) -> str:
        """Null hypothesis"""
        return self._null

    @property
    def alternative(self) -> str:
        return self._alternative

    def __str__(self) -> str:
        name = "" if not self._name else self._name + "\n"
        msg = (
            "{name}H0: {null}\n{name}H1: {alternative}\nStatistic: {stat:0.4f}\n"
            "P-value: {pval:0.4f}\nDistributed: {dist}"
        )
        return msg.format(
            name=name,
            null=self.null,
            alternative=self.alternative,
            stat=self.stat,
            pval=self.pval,
            dist=self.dist_name,
        )

    def __repr__(self) -> str:
        return (
            self.__str__()
            + "\n"
            + self.__class__.__name__
            + ", id: {0}".format(hex(id(self)))
        )
